Excavating machines

ABSTRACT

A hydraulic system including a hydraulic cylinder operated by a pressure-actuated servo-controlled operating valve and a crossover valve to interconnect the fluid lines leading to the hydraulic cylinder operated by an electrically controlled valve interposed in a pressure line leading to the operating valve.

United States Patent Inventors App]. No.

Filed Patented Assignee Priority Kjell Anton Landaeus Lund;

Karl Oscar Olsson, Eslov, both of Sweden 877,633

Nov. 18, 1969 Dec. 28, 1971 Akermans Verkstad Aktiebolag Eslov, Sweden Nov. 29, 1968 Sweden EXCAVATING MACHINES 4 Claims, 1 Drawing Fig.

U.S.C1

1nt.C1

Field of Search ..Fl5b 11/08, FlSb 13/043 [56] References Cited UNITED STATES PATENTS 2,219,967 10/1940 Thiry 91/437 3,133,474 5/1964 Reichelet a1... 91/45OX 3,220,318 11/1965 McGuire 91/461 3,313,316 4/1967 Thomas... 91/437 X 3,472,127 10/1969 Scheidt 91/437 3,508,400 4/1970 Mercier 91/461 Primary Examiner--Martin P. Schwadron Assistant Examiner-Irwin C. Cohen Attorney-Beveridge & De Grandi ABSTRACT: A hydraulic system including a hydraulic cylinder operated by a pressure-actuated servo-controlled operating valve and a crossover valve to interconnect the fluid lines leading to the hydraulic cylinder operated by an electrically controlled valve interposed in a pressure line leading to the operating valve.

PATENTElJflEczelsm I 3,630,121

mvsNT R luau. LANDAEUS 4 KARL OSCAR OLSSON by 45mm #DAQML 05% sxcxvxrmc MACHINES This invention relates to excavating and like machines having a boom, a hydraulic power unit-for raising and lowering the boom, an operating valve for controlling the supply of pressure medium to the hydraulic power unit of the boom, and a servo circuit including an operating lever for adjusting the operating valve.

In the use of hydraulically operated excavating machines for the removal of a soft surface layer from a hard base, for example so-called clearing of rocky ground, problems arise since it is possible for the hydraulically operated boom only with great difficulty to follow the outlines of the base, from which results that the surface layer is but unsatisfactorily removed from recesses in the base and that the entire excavating machine is raised when elevations of the ground are encountered. It is thus desired to have the possibility of releasing the boom from the influence of the hydraulic power unit so that the bucket bears against and follows the base only under the weight of the boom, the bucket arm and the bucket with ancillary parts. In this connection, however, an important requirement is that this measure shall not disturb the normal function of the hydraulic power unit of the boom and that it shall be possible instantaneously to make the hydraulic power unit operative again.

These desiderata and requirements are satisfied by the present invention in that a valve mechanism is connected in the servo line to the operating valve of the hydraulic power unit of the boom and that said valve mechanism is preferably adjustable by means of an electric switch into either of two positions, and in one of said two positions the operating valve of the hydraulic power unit of the boom is directly operable by means of the operating lever while in the other of said two positions the operating valve of the hydraulic power unit of the boom is directly operable by means of the operating lever when said lever is brought into position for raising of the boom, but a further valve is connected when the operating lever is brought into position for lowering of the boom and a given minimum pressure has'been attained, said valve being adapted to short circuit the operating lines of the hydraulic power unit of the boom so that the boom with ancillary parts will bear against the base under its own weight.

The invention will be more fully described inthe following, reference being has to the accompanying drawing which by means of recognized symbols illustrates a circuitry for hydraulically operating the boom of an excavating machine.

The circuitry illustrated in the drawing is adapted for use in a conventional hydraulically operated excavating machine having a subframe, a superstructure arranged for rotation on the subframe, a boom pivoted to the superstructure, and a bucket arm with bucket arranged on the boom.

A hydraulic power unit is arranged between the superstructure and boom of the excavating machine, and upon extension and shortening the hydraulic power unit respectively raises and lowers the boom. The hydraulic power unit 10 is connected over lines 11 to a main directional valve 12. The valve 12 is of the conventional type and can occupy three different main positions as well as intermediate positions. It is connected to a main pump 13 and a tank of pressure medium 14. Arranged to operate the main valve 12 is a servo circuit including a servo pump 15, a tank 16 and an operating lever 17 by which either side of the main valve 12 can be connected to the servo pump for moving the valve member of the main valve 12 in the desired direction. The arrangement as hitherto described is conventional in excavating machines.

A directional valve 18 is connected to one of the servo lines leading to the operating valve 12, more particularly the line which is connected to the servo pump upon lowering of the boom. The valve 18 is electrically operable by means of a switch 19 and can occupy two different positions. In the position illustrated in which the switch 19 is not cut in, the servo pressure medium is led directly to the main operating valve 12, as will appear from the drawing. When the switch 19 is cut in, however, the servo pressure medium is led to a directional valve 20 which is hereinafter termed floating position valve. This valve 20 is so loaded that it is actuated only when the servo pressure has reached a predetermined minimum pressure, for instance 40-50 kp/sq.cm. When this pressure is reached the piston in said valve 20 is moved from the position shown in the drawing so that the two lines 11 are connected to one another and also to the tank 14. When the directional valve 18 occupies the position shown in the drawing it will be seen that the valve 20 is connected to the tank 14.

In use the boom is operated by the illustrated arrangement in the following way. Upon raising of the boom the operating lever 17 is moved to the right, causing servo pressure medium to flow from the servo pump to the upper end of the valve l2 which is thus moved downwards so that pressure medium flows from the main pump through the valve 12 and one line 11 to the hydraulic power unit 10. Upon lowering of the boom, on the other hand, the operating lever 17 is moved to the left so that servo pressure medium flows to the lower end of the valve 12, causing pressure medium from the main pump to be supplied to the hydraulic power unit 10 through the other line 11. lfit is desired to remove a soil layer from a hard base, so-called clearing of rocky ground, the switch 19 is engaged, which will actuate the directional valve 18 in such a way that the valve member is moved in an upward direction and the servo line is connected to the valve 20, while the connection with the valve 12 is interrupted. Upon raising of the boom no difference arises in relation to the former case, but upon lowering of the boom servo pressure medium flows through the valve 18 to the floating position valve 20 which then short circuits the lines 11, as earlier stated, and interconnects them with the tank 14. As a result, the hydraulic power unit 10 will not act upon the boom any longer and the bucket will therefore bear against the base under the weight of the boom, the bucket arm and the bucket as well as ancillary parts, making it possible to carry out efficient clearing.

What we claim and desire to secure by Letters Patent is:

1. For use in an excavating machine having a boom, a hydraulic cylinder adapted to be connected to a boom, a source of pressure fluid, a pressureactuated servo-controlled operating valve operable to selectively direct pressure fluid through a first hydraulic line to one end of the cylinder to raise the boom and through a second hydraulic line to the other end of the cylinder to lower the boom, and a servomechanism for actuating the operating valve, said servomechanism including a manually operated servo valve for selectively directing fluid under pressure through a first conduit connected to the operating valve to condition the operating valve to raise the boom and a second conduit connected to the operating valve to conditionthe operating valve to lower the boom, the improvement comprising, crossover conduit means connecting said first and said second hydraulic lines, pressure-actuated crossover valve means connected in said crossover conduit, and selectively operable valve means connected in said second conduit and movable between a normal position in which pressure fluid in said second conduit is directed to said operating valve to condition said operating valve to lower the boom, and a crossover position directing fluid in said second conduit to said pressure-actuated crossover valve to interconnect said first and second hydraulic lines to permit downward movement of the boom independent of fluid pressure in said second conduit.

2. in the excavating machine as defined in claim I, the further improvement wherein said pressure-actuated crossover valve is preloaded in a closed direction, whereby a predetermined pressure in said crossover channel is required to actuate the valve to interconnect said first and second hydraulic lines.

3. In the excavating machine as defined in claim I, the further improvement wherein said selectively operable valve means is an electrically controlled two-position valve.

4. For use in an excavating machine having a boom, a hydraulic cylinder adapted to be connected to a boom, a source of fluid pressure, and a hydraulic control system for directing fluid under pressure to said cylinder for raising and lowering the boom, and improvement wherein said hydraulic control system comprises, in combination, a pressure-actuated servo-controlled operating valve operable to selectively direct pressure fluid through a first hydraulic line to one end of the hydraulic cylinder to raise the boom and through a second hydraulic line to the other end of the hydraulic cylinder to lower the boom, a servomechanism for actuating the operating valve, said servomechanism including a manually operated servo valve for selectively directing fluid under pressure through a first conduit connected to the operating valve to condition the operating valve to raise the boom and a second 

1. For use in an excavating machine having a boom, a hydraulic cylinder adapted to be connected to a boom, a source of pressure fluid, a pressure-actuated servo-controlled operating valve operable to selectively direct pressure fluid through a first hydraulic line to one end of the cylinder to raise the boom and through a second hydraulic line to the other end of the cylinder to lower the boom, and a servomechanism for actuating the operating valve, said servomechanism including a manually operated servo valve for selectively directing fluid under pressure through a first conduit connected to the operating valve to condition tHe operating valve to raise the boom and a second conduit connected to the operating valve to condition the operating valve to lower the boom, the improvement comprising, crossover conduit means connecting said first and said second hydraulic lines, pressure-actuated crossover valve means connected in said crossover conduit, and selectively operable valve means connected in said second conduit and movable between a normal position in which pressure fluid in said second conduit is directed to said operating valve to condition said operating valve to lower the boom, and a crossover position directing fluid in said second conduit to said pressure-actuated crossover valve to interconnect said first and second hydraulic lines to permit downward movement of the boom independent of fluid pressure in said second conduit.
 2. In the excavating machine as defined in claim 1, the further improvement wherein said pressure-actuated crossover valve is preloaded in a closed direction, whereby a predetermined pressure in said crossover channel is required to actuate the valve to interconnect said first and second hydraulic lines.
 3. In the excavating machine as defined in claim 1, the further improvement wherein said selectively operable valve means is an electrically controlled two-position valve.
 4. For use in an excavating machine having a boom, a hydraulic cylinder adapted to be connected to a boom, a source of fluid pressure, and a hydraulic control system for directing fluid under pressure to said cylinder for raising and lowering the boom, and improvement wherein said hydraulic control system comprises, in combination, a pressure-actuated servo-controlled operating valve operable to selectively direct pressure fluid through a first hydraulic line to one end of the hydraulic cylinder to raise the boom and through a second hydraulic line to the other end of the hydraulic cylinder to lower the boom, a servomechanism for actuating the operating valve, said servomechanism including a manually operated servo valve for selectively directing fluid under pressure through a first conduit connected to the operating valve to condition the operating valve to raise the boom and a second conduit connected to the operating valve to condition the operating valve to lower the boom, and selectively operable crossover means connected between said first and said second hydraulic lines, said selectively operable crossover means including pressure-actuated valve means connected in said second conduit, and selectively operable means for directing pressure fluid from said second conduit to said pressure-actuated valve means to interconnect said first and second hydraulic lines only when said manually operated servo valve is positioned to direct pressure fluid to said second conduit. 